1. Field of the Invention
The present invention relates to a fuel injection pump device for an internal combustion engine, and more particularly to a fuel injection pump device having an altitude compensating unit for controlling an amount of fuel injected into the engine in response to change in altitude or atmospheric pressure.
2. Description of the Prior Art
Air density is gradually decreased with increase in altitude, or as approaching a high land from a level land, and an actual amount of air introduced into the engine is decreased in the high land. If the amount of fuel injected into the engine is maintained constant, the air-fuel ratio will be lowered and smoke will be increased in the high land. A prior art fuel injection pump device is provided with an altitude compensating unit which continuously controls the amount of fuel injected into the engine in response to change in the altitude or atmospheric pressure, to restrain the smoke to a constant level. However, this causes the engine output to be considerably decreased in the high land. In addition, upon adjustment of a pump unit of the fuel injection pump device and upon check or inspection of the engine performance in the level land, the continuous change in the amount of injected fuel in response to the change in atmospheric pressure causes the amount of fuel injected by the pump unit and the engine performance to be changed in accordance with the atmospheric pressure at that time. Accordingly, disadvantages occur that the adjustment is required to be made to the pump unit and the assessment is required to be made to the engine performance with the pressure around the altitude compensating unit adjusted to a predetermined value, or in consideration of the atmospheric pressure.